The invention relates to a compact zoom lens having a bending-type optical system.
Recently, image forming optical devices such as digital still cameras or digital camcorders using solid state image sensors, for example, charge coupled devices (CCD) or complementary metal-oxide semiconductors (CMOS) for converting an optical image into an electric signal are widely and rapidly used. Also, as portability is regarded as important, a demand for increased miniaturization of the device is present. As one of designs for decreasing the thickness of a camera, a zoom lens having a structure of refracting an optical path within an optical system so that the thickness of a camera is not influenced by the number of lens units is employed.
The bending-type optical system is implemented, for example, by using a prism that can change an optical path by 90°. The thickness of a camera is determined by the overall thickness of lenses, which are at an object side of the prism, and an effective diameter of a lens group arranged at an image side of the prism. In achieving the miniaturization of the device by reducing the thickness and the diameter, a design which may facilitate prevention of the excessive overall length of the optical system and correction of aberration as well, by appropriately setting the number of lenses arranged from the prism to the image side, is needed.